Manchester United's chief executive, David Gill, last night rounded on the figurehead of the Red Knights group that claims to be preparing a bid for the club. Keith Harris, the former Football League chairman whose Seymour Pierce stockbroker has been at the centre of several club takeovers, was dismissed by Gill as a publicity seeker.

"Keith Harris will go anywhere there is publicity and we accept that; it's his modus operandi," said Gill. "But if you look at his track record in football it is nothing to write home about."

Gill was referring to Harris's recent attempts to find buyers for football clubs. He has not completed a takeover deal since putting Thaksin Shinawatra in control of United's rival Manchester City almost three years ago. Even that was undone after 14 months when it became clear that Thaksin's conviction on charges of corruption meant he would fail the Premier League's fit and proper persons test.

However, Gill's attack on the man fronting the Red Knights shows Old Trafford is feeling the pressure from the group of wealthy bankers and the fans' green-and-gold protests. "It affects us," he conceded.

Despite the hostility towards Harris, prompted by the latter's call last month for supporters to boycott the club, Gill was complimentary about the other figures involved in the Red Knights group. They include blue-chip corporate notables such as the former United director and Goldman Sachs chief economist, Jim O'Neill, and the club's former legal adviser, the Freshfields partner Mark Rawlinson, who he described as "credible people".

"They are not misguided," said Gill. "They have their own views and they are sensible, intelligent people. But the structure we have in place today, we can live with it. Our financial results and our financial projections demonstrate that."

United's six-month figures to the year-end 2009 were released on Tuesday and reflected a much-improved picture on the previous year, with pre-tax earnings of £56.5m, up from £36.5m.

Speaking at the Soccerex conference in an interview with Matt Lorenzo, who has been a friend of O'Neill's since their time together at Sheffield University, Gill insisted the Glazers would not relinquish control of the club. "The [Glazer] family aren't sellers," he said. "There has been no indication to me they want to sell. The Red Knights can come with a proposal but they won't sell the asset. It won't go anywhere."

Despite a doubling of the membership of the Manchester United Supporters' Trust movement on the back of the Red Knights' announcement, Gill was dismissive of their scheme. They hope to bring together 40 high-net-worth individuals, each contributing upwards of £20m towards the buyout, the balance of a £1bn offer being made up of debt. "I don't know how it would work," he said. "I've been involved in football since 1997 and travelled a lot with Manchester United. I've been to a lot of clubs in Europe and the best clubs, the better-run clubs have clear, single decision-making [processes], it's quick and efficient.

"I don't see how if you've got a number of very wealthy people being involved – they don't become wealthy through luck – those sort of people want to be involved in the decision making,

"The key clubs, [Roman] Abramovich at Chelsea, Mansour [Al-Nahyan] at Manchester City, [Silvio] Berlusconi in Milan, even the key decision maker at Madrid is not all those fans, it's the president. I'm not sure what the endgame is but the endgame is irrelevant because the owners are long-term investors and want to keep the club for many years to come."

One difference between the Glazers and the examples Gill cited, with the exception of Mansour, is their low profile. Yet Gill made a virtue of that. "They watch every game on the television and I think they have been supportive," he said. "We've got many examples of owners who have come in and run a club, picked the team, been very visible at the ground and in the press.

"They've taken the view that they're not here to do that. They've got a good management team in place, a fantastic manager in Sir Alex Ferguson. In order to control the asset and get the most of the asset they have those people there to manage the business that they've bought but I don't think their lack of attendance should be taken that they're not very passionate about the club and very interested in how they do. That isn't the case."

In the past Gill had been highly critical of the leveraged Glazer business plan that has now caused so much anger among the club's supporters. But despite the fact this is at the root of the current rebellion by fans, Gill defended the American owners.

"When they first approached us in September 2004, we looked at it [their offer] and we felt at the time that the level of debt they were proposing and business plan underpinning that debt were too aggressive," he said.

"We were public in terms of our opposition to that and they revisited those plans, changed the structure of the financing, revisited the business plans underpinning that financing and that culminated in the takeover in 2005.

"We didn't as a board, recommend the offer, it didn't go with a board recommendation but as directors we were obliged to put it to the shareholders and they accepted that and so we move on."

Gill's challenge is that a significant number of fans will not move on until the Glazers move out.